The invention relates to a projectile base for carrier projectiles carrying submunition, with the projectile base including a base body having a front section with a cylindrical outer surface, a tail section with a conically tapered outer surface and a base plate, a rotating band disposed on the cylindrical outer surface portion of the base body, and respective cavities disposed in the respective ends of the base body with the base plate therebetween.
Such a projectile base is disclosed, for example in German patent DE No. 3,643,291. As tests have shown, such bases exhibit an unfavorable deformation behavior. This leads to problems in sealing and in the transmission of spin by the rotating band. The gas breakthrough that is unavoidable at high gas pressures (loss of contact between rotating band and tube wall) leads to continuous opening and closing of the sealing gap during passage through the tube and thus to the excitation of oscillations of the projectiles resulting in increased tube wear.
The cause of these sealing problems is that the axial force components acting on the tail of the projectile during firing cause the base plate to be axially bent, and is associated with radial widening of the front projectile base body and radial constriction of the rear projectile base and the rear rotating band region. The radial deformation by the axial force components during firing is superposed on the radial deformations due to the simultaneously acting radial force components. This superposition is the cause of the resulting radial deformation of the projectile base.
The radially acting forces result, on the one hand, from the gas pressure which extends to the rear end of the rotating band and from the rotating band pressure. These forces lead to radial constriction of the base body over its entire length. If, the superposition of both deformation states results in radial constriction at the rear edge of the rotating band, there will be loss of contact between the rotating band and the tube. This exposed gap area fills with gas which is equivalent to an increase in the radial force acting on the base body. The result is further enlargement of the radial constriction in the rotating band region and finally a complete gas breakthrough.
Furthermore, U.S. Pat. No. 4,327,643 discloses explosive projectiles whose base plates are curved at the tail end. However, the interior of the projectiles is filled with an explosive so that the base plate cannot be deformed much in the axial and radial directions (if a cavity were present in the interior of these projectiles, the projectile base, due to its thin walls and the extreme curvature of its base and absent the radial support by the explosive, would collapse under the gas pressure existing up to the rotating band during firing).